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Cholesterol thermal degradation in the presence of oxidants and fatty acids : model-system study

Gislaine Chrystina Nogueira de Faria
Total Authors: 1
Document type: Doctoral Thesis
Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia de Alimentos
Defense date:
Examining board members:
Antônio Eduardo Miller Crotti; Lilian Regina Barros Mariutti; Mônica Roberta Mazalli; Eduardo Vicente
Advisor: Neura Bragagnolo

One of the pathways of cholesterol degradation, when it is submitted to heat, is the production of cholesterol oxidation products (COP). Those compounds have been associated to several biological effects and degenerative diseases and their formation can be influenced by other substances, such as antioxidants and fatty acids. The influence of the antioxidants is related to their mechanisms, which can act in the initiation and or propagation phases of the lipid oxidation. The influence of the fatty acids is associated to their degree of unsaturation, because of the free radical formation. In order to verify the cholesterol behavior during heating with the influence of those substances, model systems containing cholesterol and ß-carotene, TBHQ, vitamin E, stearic acid or linolenic acid, were studied. The model systems were heated at 140, 180 and 220 °C until at least 75% of cholesterol was degraded. The amount of cholesterol, COP and 7-hydroperoxycholesterol ¿ an intermediate compound of COP formation ¿ was evaluated during heating process. Cholesterol degradation was observed at all studied temperatures, occurring at a velocity directly proportional to the temperature increase, totalizing approximately 8 min at 220 °C, 20 min at 180 °C and 1 h at 140 °C. According to the obtained results, COP are formed reaching a maximum content and after that are degraded, but at 140 °C, the maximum was reached only at the systems containing fatty acids. The presence of fatty acids accelerated COP formation; however, the systems containing linolenic acid showed lower total content at all studied temperatures, on the other hand, the systems containing stearic acid showed lower content only at 220 °C, when compared to the pure cholesterol system. Except TBHQ, at 140 °C, all antioxidants were able to reduce and/or delay the maximum amount of total COP during heating (AU)